HFSS and UWB antenna

Hi all,
I decided to simulate UWB antenna with HFSS, Is it better to use fast or discrete? Or it's better to use CST? why?

"fast" takes less time while "discrete" takes longer. To have first impression, fast can be used. for more accuracy, discrete is used.

For UWB, CST takes much less time. This is due to the fact that it uses time domain signal and then converts it to freqeuency domain signal. It does not do the calculations at different frequency points.

Thanks Shmeemkabir,
but in CST I don't know how much set thickness, it's enough 10% thickness of substrate?

I really didn't understand, what thickness you refer to.